304 Mr. Foulion's further experiments upon 



6. EXPEKIMENTS IN 1890 UPON CaTOCALA FRAXINI. 



Similar experiments were conduoted on this species, 

 but I cannot now lay my hands on the notes. However, 

 I remember clearly that the results were similar to those 

 obtained by Miss Gould in the same year, except that 

 my light larvae did not exhibit a tendency to become 

 greenish, but were very light brown. My results were, 

 in fact, similar to those obtained in the case of C. clocata, 

 and both these species may be regarded as extremely 

 sensitive to the colours of their surroundings ; while the 

 other Catocalidcs investigated, including C. nupta, tested 

 by Miss Gould, are far less susceptible. It is very 

 remarkable that closely allied larvae, belonging to the 

 same genus, should differ so widely in the degree to 

 which they are susceptible. It is possible, however, 

 although not probable, that experiments upon larger 

 numbers may modify these conclusions as regards Cato- 

 cala. It is, however, known that the same difference 

 obtains in the pupae of certain species of the genus 

 Papilio (Phil. Trans. Koy. Soc, 1887, B, p. 408). 



We now pass to more numerous and satisfactory 

 experiments upon the larvae of Geometrce. 



7. Experiments in 1886 upon the larv^ and pup^ of 

 Ennomos angularia. 



The ova were obtained from a captured female, and I 

 believe that all the larvae hatched from one lot of eggs. 

 The food-plant employed in all cases was elm. The 

 experiments were arranged May 8 and 9. 



I. Dark surroundings. — The twigs of elm were intro- 

 duced with the leaves. The larvae were compared June 12, 

 when there were 23 alive, and all decidedly darker than 

 than those of II. By June 15 they were spinning up 

 rapidly. I am not sure whether there were more twigs 

 added in addition to those bearing the leaves, but probably 

 not, considering the relative darkness of III. 



II. Green surroundings. — The leaves alone of elm were 

 used. 7 larvae were alive on June 12, and much lighter 

 than in I. 



III. Darkness. — The same food-plant, twigs as well as 

 leaves, was covered by a cylinder enclosed in two thick- 

 nesses of black tissue-paper. On June 19 they were 



